1. The Field of the Invention
This invention relates to optical communication systems. More particularly, embodiments of the present invention relate to an optical switch using a flexure pivot.
2. Relevant Technology
Optical communication systems are becoming a substantial and fast-growing constituent of traditional communication networks. Optical communication systems are particularly advantageous because they provide the capability to convey information at a much higher transmission rate than traditional electrical wire systems. Moreover, optical-based communications systems are less susceptible to certain types of noise, such as from lightning and electromagnetic radiation, can be implemented with lighter weight cable, and provide better signal quality over extended distances compared to electrical wire systems.
Optical communication systems use waveguides to transfer light from one location to another. A waveguide is a device that generally confines and guides a propagating electromagnetic wave, such as light. An example of a waveguide is an optical fiber, which is typically a thin, circular, transparent fiber that guides light down the length of the fiber.
In addition to using optical fibers for guiding a light signal, other optical devices are used to further manipulate the light signal. In particular, devices are used to connect a fiber or a fiber optic component to another component or another fiber. Such devices typically provide mechanical support for connecting waveguides while allowing the transmittance of the desired light. One example of such an optical interconnection device is an optical switch. In optical telecommunication systems, optical switches can be used to switch light from one input optic fiber to one or the other of two output optic fibers, for example. This type of switch is often referred to as a 1.times.2 switch. Other switch types may use more than one input and exit fiber. These are designated as N.times.N or N.times.M switches. For example, a 1.times.8 switch has one input and eight potential outputs.
Opto-mechanical switches physically move fibers or optical components so they are in a position to transfer light to the desired output fiber. Moveable optical components can be a mirror, a lens assembly, a prism, a filter, or any similar type of optical component that can be used to reflect, refract, retransmit or otherwise manipulate a light signal, as well as a fiber. In a typical configuration, an optical switch may include a graded index ("GRIN") lens or equivalent aspheric lens to expand and collimate the light beam received at an input fiber, or to collect and direct the light to an output fiber. In one switch position, the light beam may be directly passed through a receiving GRIN lens to a first output fiber via another GRIN lens. The switch can be activated to a second switch position that causes an optical component (mirror, filter, prism, etc.) to be placed in the path of the incoming collimated light beam. Depending on the position and type of the optical component element, the light beam is redirected towards a selected output fiber. A feature of opto-mechanical switches is that the switching operation depends upon the ability to move an optical component between switch positions.
Since these switches depend on mechanical movement, they necessarily rely upon moving parts. This can result in a variety of problems. In particular, the action of an opto-mechanical switch must be precise and accurate, due to the extremely small physical dimensions of typical optical transmission media. For example, in typical applications an optical fiber as small as 8 micrometers (8 .mu.m) in diameter must be re-imaged on a similarly sized fiber after reflection, refraction, or transmission by or through the moveable component operated by the switch. A slight misalignment between the moveable component and the input and/or output fiber can result in the loss of signal integrity. Such misalignment might arise from machining tolerances or wear of mating parts, for example. Precision must be maintained even when the switch is being operated at high switching speeds, and over long periods of time.
Other factors contribute to the problem of maintaining optical alignment within an opto-mechanical switch. Communications applications often subject an optical switch to a wide range of adverse environmental conditions, including wide ranges in temperature, pressure and humidity. Operating conditions may also be extreme in other respects. For instance, some switches may be exposed to mechanical vibrations that can affect the optical alignment of the switch. Applications also may require that the optical switch be operable for hundreds of thousands of cycles, and after long periods of idleness. Regardless of the environmental circumstances however, the switch must still maintain accurate and precise optical alignment.
Various approaches for providing a suitable switching mechanism for use in optical switches have used mechanical sliders, rollers, pivot assemblies, etc., none of which have been entirely satisfactory. For example, U.S. Pat. No. 5,594,820 discloses an opto-mechanical switch in which the moveable optical component is carried on a flexible suspension unit by two generally parallel flexures that flex in common. An actuator mechanism applies an effort at the end of the flexures that is opposite to the end attached to the anchorage block. This bends the flexures, which moves the optical component to perform the switching operation. However, a suspension mechanism with this general configuration can be sensitive to vibration, and thus may not be appropriate for use in certain environments.
Other switches utilize sliding elements to provide physical actuation of the switch mechanism. Such approaches are disclosed in U.S. Pat. Nos. 4,790,621 (the '621 patent) and 4,303,303 (the '303 patent). The '621 patent discloses an optical switch with a sliding element switch with spring latches. The '303 patent discloses an optical switch in which a parallelogram prism is moved on a sliding block between two stops. However, switches that rely on such sliding mechanisms undergo frictional contact, which produces wear. Often, such devices require ongoing maintenance, such as lubrication, and they may have shorter operational lifetimes.
Given the problems with the prior art solutions, there is a need in the art for an optical switch that allows for precise and accurate positioning of the switch's movable optical component. In addition, it is desirable to have an optical switch in which precise and accurate operation and alignment of the movable optical component(s) can be achieved at one or more switch positions. Moreover, such alignment should be maintained throughout the entire switching motion and at high switching speeds. It is also desirable that the highly accurate and reproducible operation of the optical switch be accomplished within adverse environmental conditions, such as wide temperature and humidity ranges, vibration, and after long periods of inactivity. Finally, the switch should be capable of undergoing a high number of switching cycles without failure or requiring ongoing maintenance.